The Cutting Edge

ARACEAE. "Xanthosoma jacquinii Schott, nom. illeg." is mistakenly given as
a synonym of X. undipes (K. Koch & C. D. Bouché) K. Koch; it should instead
appear in the synonymy of X. sagittifolium (L.) Schott. This error traces to our
misunderstanding of Koch’s remarks in Bonplandia (Hannover) 4: 3 (1856), where Alocasia
undipes K. Koch & C. D. Bouché was formally transferred to Xanthosoma.
There, Koch makes the case that his X. undipes is identical to X. jacquinii
"in hort. Schoenbr. nec in melet."; in other words, the plants grown by Schott at
Schönbrunn under the name X. jacquinii were misidentified (at least in Koch’s
view), and actually represented X. undipes. We got this right, taxonomically speaking,
in applying the name X. undipes based on Schott’s color plate labeled as
X. jacquinii. Nomenclaturally, however, X. jacquinii is a superfluous
renaming of Arum xanthorrhizon Jacq. (presumably to avoid a near-tautonym), for which
the correct name in Xanthosoma is X. xanthorrhizon (Jacq.) K. Koch. The Manual
lists X. xanthorrhizon as a synonym of X. sagittifolium (correctly, we think),
and that is where X. jacquinii must also be (automatically) referred.